IO-390-D Series Engine Maintenance Manual
72-20
© 2020 Avco Corporation. All Rights Reserved
Page 184
March 2020
IO-390-D Series Engine Maintenance Manual
(8)
Remove the test plate P/N ST-483 and gasket. Discard the gasket.
(9)
Install the propeller governor on the engine per the “Propeller Governor Instalation”
procedure in this chapter for engines with a front-mounted propeller governor or in
Chapter 72-25 for engines with a rear-mounted propeller governor.
28.
Propeller Governor Removal (Engines with Front-Mounted Propeller Governor Drives)
A.
Remove the nuts lock washers and washers from the studs in the propeller governor
mounting pad. Discard the lock washers.
B.
Remove the propeller governor and governor gasket. Discard the gasket.
29.
Propeller Governor Installation (Engines with Front-Mounted Propeller Governor Drives)
A.
If a cover or mask is installed on the propeller governor mounting pad, remove the nuts and
cover or mask.
B.
Install the propeller governor in accordance with the aircraft manufacturer’s instructions.
30.
Crankshaft-to-Camshaft Timing Check
NOTICE:
This timing check is completed on a partially or fully assembled engine without
removing the accessory housing.
A.
Make sure the ignition and all electrical switches are OFF.
B.
Disconnect all spark plug leads.
C.
Disconnect the starter.
D.
Remove the top spark plug on Cylinder 1 as per the “Spark Plug Removal” procedure in
Chapter 74-20.
E.
Remove the rocker box cover on Cylinder 2 as per the “Exhaust Valve and Guide Inspection”
procedure in Chapter 72-30.
F.
Rotate the crankshaft to position Cylinder 1 piston at Top Dead Center (TDC) on the
compression stroke.
G.
Monitor the movement of the intake and exhaust valves in Cylinder 2 as you turn the
crankshaft to move the piston just past TDC of Cylinder 1.
H.
The crankshaft-to-camshaft timing is correct if the intake valve and the exhaust valve in
Cylinder 2 just begins to close as the intake valve starts to open as the piston in Cylinder 1
goes over TDC on compression.
I.
If this simultaneous opening and closing of the intake and exhaust valves just past TDC does
not occur, the crankshaft-to-camshaft timing is not correct. Repeat this timing check. If the
results are the same, remove the accessory housing and complete a check of the alignment of
the crankshaft idlers gears per the ”Crankshaft Idler Gear Installation” section in this chapter.
J.
If the crankshaft-to-camshaft timing is correct:
(1)
Install the rocker box cover on Cylinder 2 with a new rocker box cover gasket as per the
“Cylinder Installation” procedure in Chapter 72-30.
(2)
Install the top spark plug on Cylinder 1 as per the “Spark Plug Installation” procedure in
Chapter 74-20.
(3)
Reconnect the starter.
(4)
Reconnect all spark plug leads
